Hydrogen can be supplied to customers connected to a hydrogen pipeline. Typically, the hydrogen is manufactured by steam methane reforming in which a hydrocarbon and steam are reacted at high temperature in order to produce a synthesis gas containing hydrogen and carbon monoxide. Hydrogen is separated from the synthesis gas to produce a hydrogen product that is introduced into the pipeline for distribution to the customers. Alternatively, hydrogen can be recovered from a hydrogen rich stream.
Typically, hydrogen is supplied to customers under agreements that require availability and on stream times for the steam methane reformer or hydrogen recovery plant. When a steam methane reformer is taken off-line for unplanned or extended maintenance, the result could be a violation of such agreements. Additionally, there are times in which customer demand can exceed hydrogen production capacity of existing plants. A storage capacity for the pipeline hydrogen or a sufficient backup is therefore very desirable in connection with hydrogen pipeline operations. However, providing a backup for hydrogen supply practically requires a large volume of hydrogen to be stored in above ground gaseous storage receivers or liquid storage tanks. The construction costs involved make such a backup storage capacity impractical.
The problem is particularly exacerbated where the hydrogen is supplied under pipeline product specification that require a hydrogen purity typically above 95% and possibly of 99.99% for ultra high purity hydrogen. Practically speaking, considering that hydrogen production plants on average have production capacities that are roughly 50 million standard cubic feet per day, a storage capacity for hydrogen that would allow a plant to be taken off-line be in the order of 1 billion standard cubic feet.
Hydrogen as well as other gases have been stored in salt caverns. Salt caverns are large underground voids that are formed by solution mining of salt as brine. Caverns are common in gulf states of the United States where demand for hydrogen is particularly high. Such hydrogen storage has only taken place where there are no purity requirements placed upon the hydrogen product. As such, contamination of the hydrogen from being stored in a salt formation is an unknown variable.
As will be discussed, inventors herein have identified the problem of increased contamination of hydrogen storage in salt caverns and have remedied contamination in accordance with the present invention in order to allow hydrogen stored within salt cavern to be delivered to a pipeline when needed under product purity specifications.